With the growing maturity of quantum computing, robust verification techniques become essential. In this paper, we introduce RuntimeSpeQ: a specification language for the runtime behaviour of quantum programs. We then propose a scheme to translate RuntimeSpeQ into runtime monitors, exploiting two types of runtime assertions. We evaluate our approach in terms of fault detection and equivalence checking capabilities as well as reusability of specifications. The results show promising runtime fault detection capabilities, with several faults detected before the final steps of the programs. Our experiments show that our monitors found 40% of faults in erroneous implementations of Quantum Phase Estimation before the final result was checked, and 90% of faults for Grover’s Algorithm. They also show no false negatives in equivalence checking. Also, across four different implementations of one case study, we found that we could reuse the same specification structure by only making minor changes, such as changing the indices pertaining to qubits or execution steps, showing the promise of reusability.
With the growing maturity of quantum computing, robust verification techniques become essential. In this paper, we introduce RuntimeSpeQ: a specification language for the runtime behaviour of quantum programs. We then propose a scheme to translate RuntimeSpeQ into runtime monitors, exploiting two types of runtime assertions. We evaluate our approach in terms of fault detection and equivalence checking capabilities as well as reusability of specifications. The results show promising runtime fault detection capabilities, with several faults detected before the final steps of the programs. Our experiments show that our monitors found 40% of faults in erroneous implementations of Quantum Phase Estimation before the final result was checked, and 90% of faults for Grover’s Algorithm. They also show no false negatives in equivalence checking. Also, across four different implementations of one case study, we found that we could reuse the same specification structure by only making minor changes, such as changing the indices pertaining to qubits or execution steps, showing the promise of reusability.
In this paper, we propose Proq, a runtime assertion scheme for testing and debugging quantum programs on a quantum computer. The predicates in Proq are represented by projections (or equivalently, closed subspaces of the state space), following Birkhoff-von Neumann quantum logic. The satisfaction of a projection by a quantum state can be directly checked upon a small number of projective measurements rather than a large number of repeated executions. On the theory side, we rigorously prove that checking projection-based assertions can help locate bugs or statistically assure that the semantic function of the tested program is close to what we expect, for both exact and approximate quantum programs. On the practice side, we consider hardware constraints and introduce several techniques to transform the assertions, making them directly executable on the measurement-restricted quantum computers. We also propose to achieve simplified assertion implementation using local projection technique with soundness guaranteed. We compare Proq with existing quantum program assertions and demonstrate the effectiveness and efficiency of Proq by its applications to assert two ingenious quantum algorithms, the Harrow-Hassidim-Lloyd algorithm and Shor's algorithm.
In this paper, we propose Proq, a runtime assertion scheme for testing and debugging quantum programs on a quantum computer. The predicates in Proq are represented by projections (or equivalently, closed subspaces of the state space), following Birkhoff-von Neumann quantum logic. The satisfaction of a projection by a quantum state can be directly checked upon a small number of projective measurements rather than a large number of repeated executions. On the theory side, we rigorously prove that checking projection-based assertions can help locate bugs or statistically assure that the semantic function of the tested program is close to what we expect, for both exact and approximate quantum programs. On the practice side, we consider hardware constraints and introduce several techniques to transform the assertions, making them directly executable on the measurement-restricted quantum computers. We also propose to achieve simplified assertion implementation using local projection technique with soundness guaranteed. We compare Proq with existing quantum program assertions and demonstrate the effectiveness and efficiency of Proq by its applications to assert two sophisticated quantum algorithms, the Harrow-Hassidim-Lloyd algorithm and Shor’s algorithm.
In this paper, we propose Proq, a runtime assertion scheme for testing and debugging quantum programs on a quantum computer. The predicates in Proq are represented by projections (or equivalently, closed subspaces of the state space), following Birkhoff-von Neumann quantum logic. The satisfaction of a projection by a quantum state can be directly checked upon a small number of projective measurements rather than a large number of repeated executions. On the theory side, we rigorously prove that checking projection-based assertions can help locate bugs or statistically assure that the semantic function of the tested program is close to what we expect, for both exact and approximate quantum programs. On the practice side, we consider hardware constraints and introduce several techniques to transform the assertions, making them directly executable on the measurement-restricted quantum computers. We also propose to achieve simplified assertion implementation using local projection technique with soundness guaranteed. We compare Proq with existing quantum program assertions and demonstrate the effectiveness and efficiency of Proq by its applications to assert two ingenious quantum algorithms, the Harrow-Hassidim-Lloyd algorithm and Shor's algorithm.
The continuous growth of quantum computing and the increasingly complex quantum programs resulting from it lead to unprecedented obstacles in ensuring program correctness. Runtime assertions are, therefore, becoming a crucial tool in the development of quantum programs. They assist developers in the debugging process and help to test and verify the program. However, while assertions can be implemented in a straightforward manner on classical computers, physical limitations of quantum computers pose considerable challenges for the evaluation of quantum assertions. Access to the quantum state of a program is limited, execution time is expensive and noise can significantly distort measurement outcomes. To address these problems, this work proposes a framework that assists developers in the evaluation of runtime assertions on real quantum computers. It translates a variety of assertions into sets of measurements, reduces execution overhead where possible and evaluates the measurement results after the execution even in the presence of noise. This approach substantially aids developers in the debugging process, enabling efficient assertion-driven debugging even in large programs. The proposed framework is available as an open-source implementation at https://github.com/munich-quantum-toolkit/debugger
Runtime assertions are a promising mechanism for testing and debugging quantum programs. But unlike the classical world, checking a quantum program that contains multiple assertions often requires using additional space or running the program additional times. For example, on current quantum hardware where mid-circuit measurement is restricted or costly, an assertion's pass/fail outcome cannot be revealed immediately. Instead, it is routed into an ancilla qubit during execution and read out by a terminal measurement. For a program with n assertions, a naive strategy uses n ancillas to learn all n outcomes, while an alternative uses one ancilla but repeats program execution over n rounds, checking one assertion per round. Both satisfy S⋅T=O(n), where S is the number of ancillas and T the number of executions: a fundamental time-space trade-off.
Can one do asymptotically better? We reveal that the answer depends sharply on the information to be learned. Reporting the outcomes of all assertions requires linear complexity, but two partial-information tasks of detecting whether any assertion fails, and of identifying the first failing assertion, require only logarithmic complexity -- an asymptotic improvement. Moreover, the checking strategies for these tasks can trade time for space in useful ways. In this work, we formalize the complexity of checking multiple assertions in a quantum program. Using this definition, we establish its landscape of asymptotic lower bounds and constructive upper bounds. We confirm via a case study on Grover's algorithm that the resource costs of constructed strategies match theoretical predictions, illustrating the practical design space for quantum programmers.
With the rapid growth of quantum computing technology, programmers need new tools for debugging quantum programs. Recent works show that assertions are a promising way for debugging quantum programs. However, there are two main drawbacks with the existing schemes. First, the existing schemes, including both statistical and dynamic assertions are only capable of asserting limited types of states, namely classical, superposition, and specific entanglement states. Second, the use cases of these assertions are limited, since the programmer has to know the exact/precise state to assert.In this work, we propose two systematic approaches for dynamic quantum state assertion and they can assert a much broader range of quantum states including both pure states and mixed states. We also introduce the idea of approximate quantum state assertion for the cases where the programmers only have limited knowledge of the quantum states. Approximate assertion is capable of checking membership in a set of states {|Ψ〉,|Φ〉,...}. While precise quantum state assertion can check a specific quantum state, approximate assertion enables a way to check whether the qubits of interest are in a super-set of some expected states, which is analogous to the well-known Bloom filter for membership checking in classical computing. Our experiments demonstrate that our systematic approaches can assert many more quantum states and can be used in various assertion locations for qubit state checking.